Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$51.31	8.478%	$55.6601	$55.66	$55.65	$55.70
Purchase #2	$6.94	7.219%	$7.441	$7.44	$7.45	$7.40
Purchase #3	$227.34	6.384%	$241.8534	$241.85	$241.85	$241.90
Purchase #4	$192.28	11.758%	$214.8883	$214.89	$214.90	$214.90
Purchase #5	$190.36	12.428%	$214.0179	$214.02	$214.00	$214.00
Purchase #6	$5.48	11.807%	$6.127	$6.13	$6.15	$6.10
Purchase #7	$80.79	12.424%	$90.8273	$90.83	$90.85	$90.80
7 purchase totals =	$754.50		$830.8150	$830.82	$830.85	$830.80